Transistor as a switch

Description

One of the most common uses for transistors in an electronic circuit is simple switches. In short, a transistor conducts current across the collector-emitter path only when a voltage is applied to the base. When no base voltage is present, the Transistor as a switch is off. ie no current can flow from the collector to the emitter. Now as the base current starts flowing, the Collector and Emitter get connected and a complete current path is provided and the current starts flowing from the collector to the emitter, and obviously, the LED gets turned on.

In the Transistor as a switch circuit we have used an LED in series with the collector and emitter so that whenever the current flows from collector to emitter, the LED glows. To provide a voltage at the base, we have used a momentary switch S2. Whenever we press the switch S2, the base of the transistor gets connected with the input power supply via a resistor R2. Here R2 is used to prevent excess current flow.